Modular Synthesizer FAQs

The purpose of this section is to offer general answers to common questions regarding modular synthesizers and synthesis.

What's the difference between audio and cv?
generally there's two sorts of input/output signal: - Audio - sound in the form of an alternating current (AC) at a frequency (pitch) and amplitude (volume) - CV - a direct current (DC) signal used to control stuff. (These are not automatically interchangeable and hence trying to use an audio signal to control a CV input parameter or trying to hear a CV may not work. there are exceptions to this though, especially more so with some module types/manufacturers.)

why am i getting constant sound from my oscillator?
- Oscillators send a signal even with no input. even if there's nothing saying what pitch to play or when to start/stop - that is done by other modules such as sequencers, VCAs etc. This is true for VCOs - they'll make a constant tone and LFOs - they'll make a constant CV (dependent on settings)

Why do i hear no sound from my VCA?
- VCAs need a CV to allow sound to pass through, unless there's an offset/initial control set to allow some audio through. In a most basic patch this CV is generally a gate triggered envelope.

Why doesn't my envelope produce a cv?
- Envelope Generators need to be triggered. This is generally done via a Gate signal, but can be a CV from pretty much anything providing enough voltage.

Why is no sound coming from my filter?
- Filters can completely silence a sound. since on a basic level filters remove frequencies from an audio signal, at certain settings a low pass filter may, for example, take all the low frequencies out of an audio signal that is just bass so nothing remains.

Why is there whistling feedback coming from my filter?
- Some filters can self-oscillate. Effectively, when certain settings are cranked up high enough a resonant filter can emit a sound even with no input, generally a relatively loud audio frequency sinewave (a feedback loop has been created).

Why is my audio getting distorted inside the modular?
- VCAs and Filters can distort when fed a sufficiently loud audio signal. this can be a very god thing - for example, feeding a moog type ladder LPF a really hot signal by putting a cranked up VCA before it in the signal path, or an feeding an analogue VCA a hot signal results in a lovely rich, warm, fuzzy, overdriven, classic 'analogue' sound.

Why does my Sample & Hold do nothing?
- Many Sample & Hold modules require an external input to sample, AND output a DC CV signal. at sufficiently high sample rate settings the CV output can be used as an audio source, but generally the output will be either a stepped sequence of CV signals if the sample is a wave or some random/pseudo-random CV signals if the input is noise or a very complex audio source.

Why does my pitch not track when i use a multiple or stack patch cables?
- To split a cv that is to control the Pitch of multiple VCOs you will need a Buffered Multiple. if you use passive multiples or stackcables, too many modules drawing from the same pitch source will affect the voltage causing tuning to be off. you can get away with only a few splits with a passive multiple/stackable, sometimes.

Why does my Buffered Multiple not work in all patch configurations?
- Buffered Multiples have designated ins/outs - these wont work like a passive multiple. you can't get a signal out of an 'in' or put an in into an 'out' with a Buffered Multiple.

Why can't i just plug anything in anywhere and get a consistent result?
- Some modules can be very sensitive to tiny changes in CV or settings, others can require quite big changes to get any significant difference in output. CVs and Audio signals can sometimes need attenuation or amplification as a result, and sometimes a DC offset/bias can be necessary to allow CV's/Audio signals to be used interchangeably. some modules have controls such as 'Gain', 'CV' amount and 'Offset' built in. otherwise, a dedicated Attenuator, a VCA or an Offset/Bias module may prove a valuable, if not essential component of a system.

Why is the volume level inside my modular so inconsistent?
- Audio can come out much louder or quieter than expected sometimes. there's a myriad of reasons, but to pick just one example, if you have certain wave forms being mixed together, phase cancellation can take place in certain circumstances, resulting in dead sounding quiet zones when sweeping through settings. your module isn't broken.

Why doesn't my ring modulator work with everything i patch into it?
- Cheaper Ring Modulators tend to be AC-coupled. this means they dont necessarily work with all CVs. for this you need a DC-coupled Ring Mod.

Can I plug the output of my modular directly into an FX pedal?
"Effects pedals" are generally designed to be used with an instrument-level signal such as guitar pickups.

As most(*) modular synthesizers are capable of levels of up to +/-15v, plugging directly into an effects pedal without prior attenuation will most likely overload its input, clipping your waveforms and resulting in distortion.

(*) In theory, most modulars should be capable of generating (and accepting) voltages almost up to their power rail voltages. An exception is Buchla 200e, which operates at line level.

Can I plug the output of an FX pedal directly in to my modular?
Short answer, yes. Longer answer: while there is nothing wrong with doing this, effects pedals are designed to work with much lower levels than those within a modular synthesizer (see above), and thus amplification will probably be desired to more closely match the levels between your external input and signals within the modular.

Reasons for matching levels:


 * Easier to mix sound sources without massively attenuating modular signals down to match external input levels.
 * Modules may be designed to "expect" a higher, modular-level signal in order to "do their thing" (eg: envelope following).
 * Signal to Noise considerations (?).

What about interfacing with external rack gear, mixers, etc?
While studio hardware is generally designed for Line-level signals, many devices will be able to handle modular level signals without distorting.